1. Field of the Invention
The present invention relates to polypeptides having laccase activity and isolated nucleic acid sequences encoding the polypeptides. The invention also relates to nucleic acid constructs, vectors, and host cells comprising the nucleic acid sequences as well as methods for producing the polypeptides.
2. Description of the Related Art
Laccases (benzenediol:oxygen oxidoreductases) are multi-copper containing enzymes that catalyze the oxidation of phenolics. Laccase-mediated oxidations result in the production of aryloxy-radical intermediates from suitable phenolic substrate; the ultimate coupling of the intermediates so produced provides a combination of dimeric, oligomeric, and polymeric reaction products. Such reactions are important in nature in biosynthetic pathways which lead to the formation of melanin, alkaloids, toxins, lignins, and humic acids. Laccases are produced by a wide variety of fungi, including ascomycetes such as Aspergillus, Neurospora, and Podospora, the deuteromycete Botrytis, and basidiomycetes such as Collybia, Fomes, Lentinus, Pleurotus, Trametes, and perfect forms of Rhizoctonia. Laccase exhibits a wide range of substrate specificity, and each different fungal laccase usually differs only quantitatively from others in its ability to oxidize phenolic substrates. Because of the substrate diversity, laccases generally have found many potential industrial applications. Among these are lignin modification, paper strengthening, dye transfer inhibition in detergents, phenol polymerization, juice manufacture, phenol resin production, and waste water treatment.
Although the catalytic capabilities are similar, laccases made by different fungal species do have different temperature and pH optima. A number of these fungal laccases have been isolated, and the genes for several of these have been cloned. For example, Choi et al. (1992, Mol. Plant-Microbe Interactions 5: 119-128) describe the molecular characterization and cloning of the gene encoding the laccase of the chestnut blight fungus Cryphonectria parasitica. Kojima et al. (1990, Journal of Biological Chemistry 265: 15224-15230; JP 2-238885) provide a description of two allelic forms of the laccase of the white-rot basidiomycete Coriolus hirsutus. Germann and Lerch (1985, Experientia 41: 801; 1986, Proceedings of the National Academy of Sciences USA 83: 8854-8858) have reported the cloning and partial sequencing of the Neurospora crassa laccase gene. Saloheimo et al. (1985, Journal of General Microbiology 137:1537-1544; WO 92/01046) have disclosed a structural analysis of the laccase gene from the fungus Phlebia radiata.
It is an object of the present invention to provide polypeptides having laccase activity and nucleic acid constructs encoding these polypeptides.